Need help with genoise sponge for swiss roll

I used Rose Levy Beranbaum's genoise sponge recipe from Cake Bible as the sponge for my buche noel. After 4 failed attempts, I'm frustrated but I haven't given up!

I baked the sponge at 400F for 10 min in a 10x5 jelly roll pan. This recipe uses both cake flour and cornstarch as well as some clarified butter. Out of the oven, the sponges have been 1) a bit rubbery, 2) had flour clumps, and 3) had tons of air bubbles on the surface. I tweaked the temperature and time a bit during each of my attempts but realized that it probably has more to do with my ability to fold in the flour. Despite carefully trying to incorporate, I can't seem to get it right. I did notice too that the eggs (which are whipped whole, not separated) may have been slightly overwhipped. Would this affect my ability to fold? Do you have any other tips or suggestions? I'm determined to get it right!

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HalfPint December 30, 2020
Sounds like a few things weren't done properly:

1. flour was not sifted enough (hence the clumps)
2. inadequate mixing/folding of flour into the egg mixture and/or the beurre-noisette (browned butter), hence the bubbles on the surface. This might also contribute to the rubbery texture.

Here is a video of Rose make a French genoise:
This segment shows how she folds in the flour and butter. Hope this helps.

Lori T. December 30, 2020
Glad to hear you haven't given up yet. So, there are a few things that might help. First, you can't really beat the eggs and sugar too much. You need all the air you can get into them, because that's all the leavening you are going to get. The reason you are getting a rubbery result though, is because you are likely getting the mixture of eggs and sugar just a wee bit too hot and the egg proteins are firming up. You really don't want that mixture to get more than lukewarm at best. The purpose is just to get the sugar dissolved a bit quicker, and it doesn't take a lot of heat to do that. And be sure your eggs are at room temperature when you start the warming process, too. You will continue to whip the eggs even after you remove them from the heat, until you get a ribbon like mixture falling from the beaters. You can try to avoid getting little flour lumps forming by using a sieve to sift the flour over the surface of the egg mixture as well, half at a time. If you see any little lumps, use your spatula or even fingers to squash those against the side of the bowl. Or if you note them in the pan before it goes into the oven, squash them. You have a lot of little bubbles because your flour wasn't quite mixed in or because you don't have quite enough firmness in the egg mixture to hold the air in for the rising. If you can, it's better to weigh your ingredients as well, rather than use cup measurements. There is enough variation in measure accuracy that it can play havoc with something like a genoise sponge if you have just a tad more or less than called for. And lower the baking temperature back to the 350F called for. At 400F, the cake is being forced to release the air long before the batter is set enough to hold on to them. This cake rises because the little air bubbles expand and try to escape. You want them trapped by the batter as that happens, but the proteins have to have a chance to set before they all escape. And bake it by the cake, not the clock. It is done when a slight touch to the center springs back, and the edges are pulling away from the pan. That can happen in 8 minutes, 10 minutes, or 12 or more. The timing given is a guide, not a law, and in the land of genoise sponges- a minute or two can make a big difference in the outcome.
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